Various liquids are marketed in bag-in-box containers connected through a suitable conduit to a dispenser at the point of use. The liquid may be, for example, syrup for soft drinks in restaurants or bars. Wine and other liquids may be dispensed in a similar manner, as may more viscous liquids such as certain condiments and salad dressing. It is desirable to have a normally closed valve at the container to assure that there is no flow of fluid until the container is connected to the line. Similarly, the line needs to be provided with a shut-off valve to avoid leakage when it is not connected to the container. Both valves should close automatically, rapidly and completely when the line connector is separated from the container.
Units for accomplishing such operation are disclosed in U.S. Pat. Nos. 4,564,132 and 5,072,756. There the valve attached to the container includes a body with a transverse wall provided with openings, and a bead around the openings. A diaphragm beneath the wall engages the bead preventing flow through these openings. There are openings through the diaphragm outside of where it engages the bead, but in the normal position where the diaphragm engages the bead there is no communication from the diaphragm openings to the openings in the wall.
When the line connector is coupled to the container valve, the diaphragm is displaced from its seat to open that valve. Also, the 25 of the line connector is forced away from its seat to an open position. 8c Both valves close when the line connector is uncoupled.
The container valve must rely entirely on the resilient force exerted by the diaphragm to be moved to and held in the closed position. This limits the size of the openings through the diaphragm and hence the flow area of the valve. If the openings are made too large, the diaphragm will not reliably assume the closed position because the cross-sectional area of the diaphragm is insufficient to create an adequate closing force. Even with small openings, the force to close the valve is limited and less than that needed for controlling the flow of certain liquids. As a result, the diaphragm-type valve is limited in its applicability and cannot be used for various viscous fluids.
It has also been proposed to construct a plastic valve member with an integral spring, as in U.S. Pat. No. 4,286,636. However, the spring in that instance is either a bellows or a coil spring with a ring base at the outer end. Such springs are relatively difficult to mold so that tooling is expensive, which raises the cost of the parts produced. The ring at the base of the spring requires excess material. The coil spring produced tends to provide an offcenter force on the valve member which detracts from its ability to seal at the valve seat.